[The effect of 2 beta-(3-hydroxypropoxy)-1 alpha, 25-dihydroxyvitamin D3 (ED-71) on callotasis in rabbit]

To evaluate the effects of 2 beta-(3-hydroxypropoxy)-1 alpha, 25-dihydroxyvitamin D3 (ED-71) on callotasis, we measured the bone mineral content (BMC) using dual energy X-ray absorptiometry (DXA) and compared the results with radiographical and histological findings, in an experimental model. Leg lengthening by callotasis was performed on 37 10-week-old Japanese white rabbits. The rabbits were divided into two groups; those in Group A (n = 19) received no medication and those in Group B (n = 18) received ED-71 (0.05 micrograms/kg body weight) twice a week following osteotomy. In both groups, from 10 days after the osteotomy, the bone was lengthened a total of 10 mm at a rate of 0.5 mm every 12 hours (1.0 mm/day) for a further 10 days. After completion of distraction, the bone mineral content (BMC) of the newly formed bone at the site of lengthening was then measured by DXA each week for 15 weeks, and the DXA findings were compared with those from radiographical and histological studies. The BMC of the newly formed bone at the site of the lengthening in both groups increased and reached a peak at two weeks after completion of the distraction. Then, the BMC gradually decreased and reached a plateau after a further 8 weeks. The BMC in Group B was significantly higher than that in Group A, and this correlated with the radiographical and histological findings. We concluded that the change in BMC at the site of the lengthening corresponded with the radiographical and histological findings, and that ED-71 administration may increase the callus formation at the site of leg lengthening.